Answer:
8 days
Explanation:
Let the number of days she rented bicycle be "b"
The total cost is fixed cost + variable cost.
Fixed cost = 55
Variables cost = 8.50 each day for b days, that is 8.50b
So, total cost is:
Total Cost = 55 + 8.50b
We know total cost is 123, so we can write:
123 = 55 + 8.50b
Now, we solve for b:

So, she rented the bicycle for 8 days